1. Technical Field
This disclosure generally relates to data security and dynamic random access memory (DRAM), and more specifically relates to providing data security for data stored in a DRAM by driving to an active state all the wordlines to clear any persistent data on power up of the DRAM chip.
2. Background Art
It has been shown that traditional DRAM chips such as those used for memory in computer laptops and other electronic devices have security issues. While it is commonly thought that the data on a DRAM chip is no longer available after powering down the chip, actually the data on the chip is persistent such that the data may still be available after power is turned off. The data, stored as a charge on a capacitor, is still available because the charge on the individual DRAM capacitors leaks off very slowly. In addition, the leak off time can be dramatically increased by chilling the DRAM device. An intruder could possibly obtain access to secure information in the DRAM.
Computer laptops or other portable computer devices are particularly vulnerable to theft of data in DRAM memory. An intruder with physical access to a laptop could potentially read all the data stored in memory even if the laptop has been powered down or placed in a password protected state such as a hibernate mode. In one scenario, this form of data theft is accomplished by powering down a laptop, and then booting it from an external drive, which runs a program that copies the entire contents of the DRAM onto this external drive. The copied data from the memory can then be mined for important data such as security keys or encryption keys. The security keys could then be used to gain access to sensitive/classified/restricted data on the hard drive that would not be available without the security keys.